Rename files in sgl kernel to avoid nested folder structure (#4213)

Co-authored-by: zhyncs <me@zhyncs.com>

sgl-kernel/python/sgl_kernel/__init__.py

@@ -0,0 +1,48 @@
+import ctypes
+import os
+
+import torch
+
+if os.path.exists("/usr/local/cuda/targets/x86_64-linux/lib/libcudart.so.12"):
+    ctypes.CDLL(
+        "/usr/local/cuda/targets/x86_64-linux/lib/libcudart.so.12",
+        mode=ctypes.RTLD_GLOBAL,
+    )
+
+from sgl_kernel import common_ops
+from sgl_kernel.allreduce import *
+from sgl_kernel.attention import lightning_attention_decode
+from sgl_kernel.elementwise import (
+    apply_rope_with_cos_sin_cache_inplace,
+    fused_add_rmsnorm,
+    gelu_and_mul,
+    gelu_tanh_and_mul,
+    gemma_fused_add_rmsnorm,
+    gemma_rmsnorm,
+    rmsnorm,
+    silu_and_mul,
+)
+from sgl_kernel.gemm import (
+    bmm_fp8,
+    cublas_grouped_gemm,
+    fp8_blockwise_scaled_mm,
+    fp8_scaled_mm,
+    int8_scaled_mm,
+    sgl_per_tensor_quant_fp8,
+    sgl_per_token_group_quant_fp8,
+    sgl_per_token_quant_fp8,
+)
+from sgl_kernel.moe import moe_align_block_size
+from sgl_kernel.sampling import (
+    min_p_sampling_from_probs,
+    top_k_renorm_prob,
+    top_k_top_p_sampling_from_probs,
+    top_p_renorm_prob,
+    top_p_sampling_from_probs,
+)
+from sgl_kernel.speculative import (
+    build_tree_kernel,
+    build_tree_kernel_efficient,
+    tree_speculative_sampling_target_only,
+)
+from sgl_kernel.version import __version__